Dehydrogenation with a nonacidic multimetallic catalyst

ABSTRACT

Dehydrogenatable hydrocarbons are dehydrogenated by contacting them at dehydrogenation conditions with a nonacidic catalytic composite comprising a combination of catalytically effective amounts of a platinum or palladium component, a ruthenium component, a Group IVA metallic component and an alkali metal or alkaline earth metal component with a porous carrier material. A specific example of the nonacidic multimetallic catalytic composite disclosed herein is a combination of a platinum component, a ruthenium component, a germanium component and an alkali metal or alkaline earth metal component with an alumina carrier material. The amounts of the catalytically active components contained in this last composite are, on an elemental basis, 0.01 to 2 wt. % platinum, 0.01 to 2 wt. % ruthenium, 0.01 to 5 wt. % germanium and 0.1 to 5 wt. % of the alkali or alkaline earth metal.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a division of my now abandoned prior, copendingapplication Ser. No. 614,402 filed Sept. 18, 1975; which in turn is acontinuation-in-part of my prior application Ser. No. 434,736 filed Jan.18, 1974 and issued Sept. 30, 1975 as U.S. Pat. No. 3,909,394; which inturn is a division of my prior, now abandoned application Ser. No.291,138 filed Sept. 21, 1972. All of the teachings of these priorapplications are specifically incorporated herein by reference.

The subject of the present invention is, broadly, an improved method fordehydrogenating a dehydrogenatable hydrocarbon to produce a producthydrocarbon containing the same number of carbon atoms but fewerhydrogen atoms. In a narrower aspect, the present invention is a methodof dehydrogenating normal paraffin hydrocarbons containing 4 to 30carbon atoms per molecule to the corresponding normal mono-olefins withminimum production of side products. Another aspect of the presentinvention involves a novel nonacidic multimetallic catalytic compositecomprising a combination of catalytically effective amounts of aplatinum or palladium component, a ruthenium component, a Group IVAmetallic component, and an alkali metal or alkaline earth metalcomponent with a porous carrier material. This composite has highlypreferred characteristics of activity, selectivity and stability when itis employed in the dehydrogenation of dehydrogenatable hydrocarbons suchas aliphatic hydrocarbons, naphthenic hydrocarbons and alkylaromatichydrocarbons.

The dehydrogenation of dehydrogenatable hydrocarbons is an importantcommercial process because of the great and expanding demand fordehydrogenated hydrocarbons for use in the manufacture of variouschemical products such as detergents, plastics, synthetic rubbers,pharmaceutical products, high octane gasoline, perfumes, drying oils,ion-exchange resins, and various other products well known to thoseskilled in the art. One example of this demand is in the manufacture ofhigh octane gasoline by using C₃ and C₄ mono-olefins to alkylateisobutane. A second example is the greatly increased requirements of thepetrochemical industry for the production of aromatic hydrocarbons fromthe naphthene component of petroleum. Another example of this demand isin the area of dehydrogenation of normal paraffin hydrocarbons toproduce normal mono-olefins having 4 to 30 carbon atoms per molecule.These normal mono-olefins can, in turn, be utilized in the synthesis ofvast numbers of other chemical products. For example, derivatives ofnormal mono-olefins have become of substantial importance to thedetergent industry where they are utilized to alkylate an alkylatablearomatic such as benzene, with subsequent transformation of the productarylalkane into a wide variety of biodegradable detergents such as thealkylaryl sulfonate type of detergent which is most widely used todayfor household, industrial, and commercial purposes. Still another largeclass of detergents produced from these normal mono-olefins are theoxyalkylated phenol derivatives in which the alkyl phenol base isprepared by the alkylation of phenol with these normal mono-olefins. Yetanother type of detergent produced from these normal mono-olefins is abiodegradable alkylsulfate formed by the direct sulfation of the normalmono-olefin. Likewise, the olefin can be subjected to direct sulfonationto make biodegradable alkenylsulfonates. As a further example, thesemono-olefins can be hydrated to produce alcohols which then in turn canbe used to produce plasticizers, synthetic lube oils and the likeproducts.

Regarding the use of products made by the dehydrogenation ofalkylaromatic hydrocarbons, these find wide application in industriesincluding the petroleum, petrochemical, pharmaceutical, detergent,plastic industries, and the like. For example, ethylbenzene isdehydrogenated to produce styrene which is utilized in the manufacturingof polystyrene plastics, styrene-butadiene rubber, and the likeproducts. Isopropylbenzene is dehydrogenated to form alpha-methylstyrenewhich, in turn, is extensively used in polymer formation and in themanufacture of drying oils, ion-exchange resins and the like material.

Responsive to this demand for these dehydrogenation products, the arthas developed a number of alternative methods to produce them incommercial quantities. One method that is widely utilized involves theselective dehydrogenation of dehydrogenatable hydrocarbons by contactingthe hydrocarbons with a suitable catalyst at dehydrogenation conditions.As is the case with most catalytic procedures, the principal measure ofeffectiveness for this dehydrogenation method involves the ability toperform its intended function with minimum interference of sidereactions for extended periods of time. The analytical terms used in theart to broadly measure how well a particular catalyst performs itsintended functions in a particular hydrocarbon conversion reaction areactivity, selectivity and stability, and for purposes of discussion herethese terms are generally defined for a given reactant as follows: (1)activity is a measure of the catalyst's ability to convert thehydrocarbon reactant into products as a specified severity level whereseverity level means the conditions used -- that is, the temperature,pressure, contact time, and presence of diluents such as H₂ ; (2)selectivity usually refers to the amount of desired product or productsobtained relative to the amount of the reactant charged or converted;(3) stability refers to the rate of change with time of the activity andselectivity parameters -- obviously the smaller rate implying the morestable catalyst. More specifically, in a dehydrogenation process,activity commonly refers to the amount of conversion that takes placefor a given dehydrogenatable hydrocarbon at a specified severity leveland is typically measured on the basis of disappearance of thedehydrogenatable hydrocarbon; selectivity is typically measured by theamount, calculated on a mole percent of converted dehydrogenatablehydrocarbon basis, of the desired dehydrogenated hydrocarbon obtained atthe particular activity or severity level; and stability is typicallyequated to the rate of change with time of activity as measured bydisappearance of the dehydrogenatable hydrocarbon and of selectivity asmeasured by the amount of desired hydrocarbon produced. Accordingly, themajor problem facing workers in the hydrocarbon dehydrogenation art isthe development of a more active and selective catalytic composite thathas good stability characteristics.

I have now found a multimetallic catalytic composite which possessesimproved activity, selectivity and stability attributes when it isemployed in a process for the dehydrogenation of dehydrogenatablehydrocarbons. In particular, I have determined that a superiordehydrogenation catalyst comprises a nonacidic combination ofcatalytically effective amounts of a platinum or palladium component, aruthenium component, a Group IVA metallic component, and an alkali metalor alkaline earth metal component with a porous carrier material in amanner such that the components are uniformly dispersed throughout theporous carrier material, the platinum or palladium and rutheniumcomponents are reduced to the corresponding elemental metallic state andthe Group IVA metal and the alkali or alkaline earth metal are presentin a positive oxidation state. This catalyst can, in turn, enable theperformance of a dehydrogenation process to be substantially improved.Moreover, particularly good results are obtained when this multimetalliccatalyst is utilized in the dehydrogenation of long chain normalparaffins to produce the corresponding normal mono-olefins withminimization of side reactions such as skeletal isomerization,aromatization, polyolefin-formation and cracking. In sum, the currentinvention involves the significant finding that a combination of aruthenium component and a Group IVA metallic component can be utilizedto beneficially interact with a platinum-containing nonacidicdehydrogenation catalyst if the metal moieties are uniformly dispersedin the catalyst and if their oxidation states are controlled ashereinafter specified.

It is, accordingly, one object of the present invention to provide anovel method for dehydrogenation of dehydrogenatable hydrocarbonsutilizing a multimetallic nonacidic catalytic composite containing aplatinum or palladium component, a ruthenium component, a Group IVAmetallic component, and an alkali metal or alkaline earth metalcomponent combined with a porous carrier material. A second object is toprovide a novel nonacidic catalytic composite having superiorperformance characteristics when utilized in a dehydrogenation process.Another object is to provide an improved method for the dehydrogenationof normal paraffin hydrocarbons to produce normal mono-olefins. Yetanother object is to improve the performance of a non-acidicplatinum-containing dehydrogenation catalyst by using a combination of aruthenium component and a Group IVA metallic component to beneficiallyinteract, stabilize and promote the platinum metal.

In brief summary, one embodiment of the present invention involves anonacidic catalytic composite comprising a porous carrier materialcontaining, on an elemental basis, about 0.01 to about 2 wt. % platinumor palladium, about 0.01 to about 2 wt. % ruthenium, about 0.01 to about5 wt. % Group IVA metal and about 0.1 to about 5 wt. % of an alkalimetal or alkaline earth metal, wherein the platinum or palladium, GroupIVA metal, ruthenium and alkali metal or alkaline earth metal areuniformly dispersed throughout the porous carrier material, whereinsubstantially all of the platinum or palladium and ruthenium are presentin the corresponding elemental metallic state, and wherein substantiallyall of the Group IVA metal and the alkali metal or alkaline earth metalare present in an oxidation state above that of the elemental metal.

A second more specific embodiment relates to a nonacidic catalyticcomposite comprising an alumina carrier material containing, on anelemental basis, about 0.05 to about 1 wt. % platinum or palladium,about 0.05 to about 1 wt. % ruthenium, about 0.05 to about 2 wt. % GroupIVA metal and about 0.25 to about 3.5 wt. % alkali metal or alkalineearth metal, wherein the platinum or palladium, Group IVA metal,ruthenium and alkali metal or alkaline earth metal are uniformlydispersed throughout the alumina carrier material, wherein substantiallyall of the platinum or palladium and ruthenium are present in thecorresponding elemental metallic state, and wherein substantially all ofthe Group IVA metal and the alkali metal or alkaline earth metal arepresent in an oxidation state above that of the elemental metal.

A third embodiment comprehends a method for dehydrogenating adehydrogenatable hydrocarbon which essentially involves contacting thedehydrogenatable hydrocarbon at dehydrogenation conditions with themulti-metallic catalytic composite defined in the first or secondembodiments.

Another embodiment involves a method for the selective dehydrogenationof a normal paraffin hydrocarbon containing about 4 to 30 carbon atomsper molecule to the corresponding normal mono-olefins. The methodessentially involves contacting the normal paraffin hydrocarbons andhydrogen at dehydrogenation conditions with a catalytic composite of thetype defined in the first or second embodiments.

Other objects and embodiments of the present invention include specificdetails regarding essential and preferred ingredients of the disclosedmultimetallic catalytic composite, preferred amounts of ingredients forthis composite, suitable methods of composite preparation,dehydrogenatable hydrocarbons that are preferably used with thiscatalyst in a dehydrogenation process, operating conditions that can beutilized with this catalyst in a dehydrogenation process and the likeparticulars. These objects and embodiments are disclosed in thefollowing detailed explanation of the various technical aspects of thepresent invention. It is to be noted that: (1) the terms "catalyst" and"catalytic composite" are used herein in an equivalent andinterchangeable manner; (2) the expression "uniformly dispersedthroughout a carrier material" is intended to mean that theconcentration of the component is approximately the same in anyreasonably divisible portion of the carrier material; and, (3) the term"nonacidic" means that the catalyst produces less than 10% conversion of1-butene to isobutylene when tested at dehydrogenation conditions, andpreferably less than 1%.

Regarding the dehydrogenatable hydrocarbon that is subjected to theinstant method, it can, in general, be an organic compound having 2 to30 carbon atoms per molecule and containing at least one pair ofadjacent carbon atoms having hydrogen attached thereto. That is, it isintended to include within the scope of the present invention thedehydrogenation of any organic compound capable of being dehydrogenatedto produce products containing the same number of carbon atoms but fewerhydrogen atoms, and capable of being vaporized at the dehydrogenationconditions used herein. More particularly, suitable dehydrogenatablehydrocarbons are: aliphatic compounds containing 2 to 30 carbon atomsper molecule, alkylaromatic hydrocarbons where the alkyl group contains2 to 6 carbon atoms, and naphthenes or alkyl-substituted naphthenes.Specific examples of suitable dehydrogenatable hydrocarbons are: (1)alkanes such as ethane, propane, n-butane, isobutanes, n-pentane,isopentane, n-hexane, 2-methylpentane, 2,2-dimethylbutane, n-heptane,n-octane, 2-methylhexane, 2,2,3-trimethylbutane, and the like compounds;(2) naphthenes such as cyclopentane, methylcyclopentane,ethylcyclopentane, n-propylcyclopentane, cyclohexane,isopropylcyclopentane, 1,3-dimethylcyclohexane, and the like compounds;and (3) alkylaromatics such as ethylbenzene, n-propylbenzene,n-butylbenzene, 1,3,5-triethylbenzene, isopropylbenzene,isobutylbenzene, ethylnaphthalene, and the like compounds.

In a preferred embodiment, the dehydrogenatable hydrocarbon is a normalparaffin hydrocarbon having about 4 to about 30 carbon atoms permolecule. For example, normal paraffin hydrocarbons containing about 10to 18 carbon atoms per molecule are dehydrogenated by the subject methodto produce the corresponding normal mono-olefin which can, in turn, bealkylated with benzene and sulfonated to make alkylbenzene sulfonatedetergents having superior biodegradability. Likewise, n-alkanes having10 to 18 carbon atoms per molecule can be dehydrogenated to thecorresponding normal mono-olefin which, in turn, can be sulfated orsulfonated to make excellent detergents. Similarly, n-alkanes having 6to 10 carbon atoms per molecule can be dehydrogenated to form thecorresponding mono-olefins which can, in turn, be hydrated to producevaluable alcohols. Preferred feed streams for the manufacture ofdetergent intermediates contain a mixture of 4 or 5 adjacent normalparaffin homologues such as C₁₀ to C₁₃, C₁₁ to C₁₄, C₁₁ to C₁₅ and thelike mixtures.

An essential feature of the present invention involves the use of anonacidic multimetallic catalytic composite comprising a combination ofcatalytically effective amounts of a platinum or palladium component, aruthenium component, a Group IVA metallic component, and an alkali metalor alkaline earth metal component with a porous carrier material.

Considering first the porous carrier material, it is preferred that thematerial be a porous, adsorptive, high surface area support having asurface area of about 25 to about 500 m² /g. The porous carrier materialshould be relatively refractory to the conditions utilized in thedehydrogenation process and it is intended to include within the scopeof the present invention carrier materials which have traditionally beenutilized in hydrocarbon conversion catalysts such as: (1) activatedcarbon, coke or charcoal; (2) silica or silica gel, silicon carbide,clays, and silicates including those synthetically prepared andnaturally occurring, which may or may not be acid treated for example,attapulgus clay, china clay, diatomaceous earth, fuller's earth, kaolin,keiselguhr, etc.; (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, zinc oxide, magnesia, thoria, boria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such asnaturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations; and (6) combination of elements fromone or more of these groups. The preferred porous carrier materials foruse in the present invention are refractory inorganic oxides, with bestresults obtained with an alumina carrier material. Suitable aluminamaterials are the crystalline aluminas known as the gamma-, eta-, andtheta-aluminas, with gamma-alumina giving best results. In addition, insome embodiments, the alumina carrier material may contain minorproportions of other well known refractory inorganic oxides such assilica, zirconia, magnesia, etc.; however, the preferred support issubstantially pure gamma-alumina. Preferred carrier materials have anapparent bulk density of about 0.2 to about 0.7 g/cc and surface areacharacteristics such that the average pore diameter is about 20 to 300Angstroms, the pore volume is about 0.1 to about 1 cc/g and the surfacearea is about 100 to about 500 m² /g. In general, excellent results aretypically obtained with a gamma-alumina carrier material which is usedin the form of spherical particles having: a relatively small diameter(i.e., typically about 1/16 inch), an apparent bulk density of about 0.2to about 0.6 g/cc (most preferably about 0.3 g/cc), a pore volume ofabout 0.4 cc/g and a surface area of about 175 m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, etc., and utilized in any desiredsize. For the purpose of the present invention a particularly preferredform of alumina is the sphere; and alumina spheres may be continuouslymanufactured by the well-known oil drop method which comprises; formingan alumina hydrosol by any of the techniques taught in the art andpreferably by reacting aluminum metal with hydrochloric acid; combiningthe resulting hydrosol with a suitable gelling agent; and dropping theresultant mixture into an oil bath maintained at elevated temperatures.The droplets of the mixture remain in the oil bath until they set andform hydrogel spheres. The spheres are then continuously withdrawn fromthe oil bath and typically subjected to specific aging treatments in oiland an ammoniacal solution to further improve their physicalcharacteristics. The resulting aged and gelled particles are then washedand dried at a relatively low temperature of about 300° F. to about 400°F. and subjected to a calcination procedure at a temperature of about850° F. to about 1300° F. for a period of about 1 to 20 hours. It is agood practice to subject the calcined particles to a high temperaturetreatment with steam in order to remove undesired acidic components suchas any residual chloride. This method effects conversion of the aluminahydrogel to the corresponding crystalline gamma-alumina. See theteachings of U.S. Pat. No. 2,620,314 for additional details.

One essential constituent of the instant multimetallic catalyticcomposite is the Group IVA metallic component. By the use of the genericterm "Group IVA metallic component" it is intended to cover the metalsof Group IVA of the Periodic Table. More specifically, it is intended tocover: germanium, tin, lead and mixtures of these metals. It is anessential feature of the present invention that substantially all of theGroup IVA metallic component is present in the final catalyst in anoxidation state above that of the elemental metal. In other words, thiscomponent may be present in chemical combination with one or more of theother ingredients of the composite, or as a chemical compound of theGroup IVA metal such as the oxide, sulfide, halide, oxyhalide,oxychloride, aluminate, and the like compounds. Based on the evidencecurrently available, it is believed that best results are obtained whensubstantially all of the Group IVA metallic component exists in thefinal composite in the form of the corresponding oxide such as the tinoxide, germanium oxide, and lead oxide, and the subsequently describedoxidation and reduction steps, that are preferably used in thepreparation of the instant composite, are believed to result in acatalytic composite which contains an oxide of the Group IVA metalliccomponent. Regardless of the state in which this component exists in thecomposite, it can be utilized therein in any amount which iscatalytically effective, with the preferred amount being about 0.01 toabout 5 wt. % thereof, calculated on an elemental basis and the mostpreferred amount being about 0.05 to about 2 wt. %. The exact amountselected within this broad range is preferably determined as a functionof the particular Group IVA metal that is utilized. For instance, in thecase where this component is lead, it is preferred to select the amountof this component from the low end of this range -- namely, about 0.01to about 1 wt. %. Additionally, it is preferred to select the amount oflead as a function of the amount of the platinum group component asexplained hereinafter. In the case where this component is tin, it ispreferred to select from a relatively broader range of about 0.05 toabout 2 wt. % thereof. And, in the preferred case, where this componentis germanium, the selection can be made from the full breadth of thestated range -- specifically, about 0.01 to about 5 wt. %, with bestresults at about 0.05 to about 2 wt. %.

This Group IVA component may be incorporated in the composite in anysuitable manner known to the art to result in a uniform dispersion ofthe Group IVA moiety throughout the carrier material such as,coprecipitation or cogellation with the porous carrier material,ion-exchange with the carrier material, or impregnation of the carriermaterial at any stage in its preparation. It is to be noted that it isintended to include within the scope of the present invention allconventional procedures for incorporating a metallic component in acatalytic composite, and the particular method of incorporation used isnot deemed to be an essential feature of the present invention so longas the Group IVA component is uniformly distributed throughout theporous carrier material. One acceptable method of incorporating theGroup IVA component into the catalytic composite involves cogelling theGroup IVA component during the preparation of the preferred carriermaterial, alumina. This method typically involves the addition of asuitable soluble compound of the Group IVA metal of interest to thealumina hydrosol. The resulting mixture is then commingled with asuitable gelling agent, such as a relatively weak alkaline reagent, andthe resulting mixture is thereafter preferably gelled by dropping into ahot oil bath as explained hereinbefore. After aging, drying andcalcining the resulting particles there is obtained an intimatecombination of the oxide of the Group IVA metal and alumina. Onepreferred method incorporating this component into the compositeinvolves utilization of a soluble decomposable compound of theparticular Group IVA metal of interest to impregnate the porous carriermaterial either before, during or after the carrier material iscalcined. In general, the solvent used during this impregnation step isselected on the basis of its capability to dissolve the desired GroupIVA compound without affecting the porous carrier material which is tobe impregnated; ordinarily, good results are obtained when water is thesolvent; thus the preferred Group IVA compounds for use in thisimpregnation step are typically water-soluble and decomposable. Examplesof suitable Group IVA compounds are: germanium difluoride, germaniumtetraalkoxide, germanium dioxide, germanium tetrafluoride, germaniummonosulfide, tin chloride, tin bromide, tin dibromide di-iodide, tindichloride di-iodide, tin chromate, tin difluoride, tin tetrafluoride,tin tetraiodide, tin sulfate, tin tartrate, lead acetate, lead bromate,lead bromide, lead chlorate, lead chloride, lead citrate, lead formate,lead lactate, lead malate, lead nitrate, lead nitrite, lead dithionate,and the like compounds. In the case where the Group IVA component isgermanium, a preferred impregnation solution is germanium tetrachloridedissolved in anhydrous alcohol. In the case of tin, tin chloridedissolved in water is preferred. In the case of lead, lead nitratedissolved in water is preferred. Regardless of which impregnationsolution is utilized, the Group IVA component can be impregnated eitherprior to, simultaneously with, or after the other metallic componentsare added to the carrier material. Ordinarily best results are obtainedwhen this component is impregnated simultaneously with the othermetallic components of the composite, Likewise, best results areordinarily obtained when the Group IVA component is germanium oxide ortin oxide.

Regardless of which Group IVA compound is used in the preferredimpregnation step, it is essential that the Group IVA metallic componentbe uniformly distributed throughout the carrier material. In order toachieve this objective when this component is incorporated byimpregnation, it is necessary to maintain the pH of the impregnationsolution at a relatively low level corresponding to about 7 to about 1or less and to dilute the impregnation solution to a volume which is atleast approximately the same or greater than the volume of the carriermaterial which is impregnated. It is preferred to use a volume ratio ofimpregnation solution to carrier material of at least 1:1 and preferablyabout 2:1 to about 10:1 or more. Similarly, it is preferred to use arelatively long contact time during the impregnation step ranging fromabout 1/4 hour up to about 1/2 hour or more before drying to removeexcess solvent in order to insure a high dispersion of the Group IVAmetallic component on the carrier material. The carrier material is,likewise, preferably constantly agitated during this preferredimpregnation step.

A second essential ingredient of the subject catalyst is the platinum orpalladium component. That is, it is intended to cover the use ofplatinum or palladium or mixtures thereof as a second component of thepresent composite. It is an essential feature of the present inventionthat substantially all of this platinum or palladium component existswithin the final catalytic composite in the elemental metallic state.Generally, the amount of this component present in the final catalystcomposite is small compared to the quantities of the other componentscombined therewith. In fact, the platinum or palladium componentgenerally will comprise about 0.01 to about 2 wt. % of the finalcatalytic composite, calculated on an elemental basis. Excellent resultsare obtained when the catalyst contains about 0.05 to about 1 wt. % ofplatinum or palladium metal.

This platinum or palladium component may be incorporated in thecatalytic composite in any suitable manner known to result in arelatively uniform distribution of this component in the carriermaterial such as coprecipitation or cogellation, ion-exchange, orimpregnation. The preferred method of preparing the catalyst involvesthe utilization of a soluble, decomposable compound of platinum orpalladium to impregnate the carrier material in a relatively uniformmanner. For example, this component may be added to the support bycommingling the latter with an aqueous solution of chloroplatinic orchloropalladic acid. Other water-soluble compounds of platinum orpalladium may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum dichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiamino-platinum, palladium chloride, palladium nitrate,palladium sulfate, etc. The utilization of a platinum or palladiumchloride compound, such as chloroplatinic or chloropalladic acid, isordinarily preferred. Nitric acid or hydrogen chloride or the like acidis also generally added to the impregnation solution in order to furtherfacilitate the uniform distribution of the metallic component throughoutthe carrier material. In addition, it is generally preferred toimpregnate the carrier material after it has been calcined in order tominimize the risk of washing away the valuable platinum or palladiumcompounds; however, in some cases it may be advantageous to impregnatethe carrier material when it is in a gelled state.

Yet another essential ingredient of the present catalytic composite is aruthenium component. It is of fundamental importance that substantiallyall of the ruthenium component exists within the catalytic composite ofthe present invention in the elemental state and the subsequentlydescribed reduction procedure is designed to accomplish this objective.The ruthenium component may be utilized in the composite in any amountwhich is catalytically effective, with the preferred amount being about0.01 to about 2 wt. % thereof, calculated on an elemental rutheniumbasis. Typically, best results are obtained with about 0.05 to about 1wt. % ruthenium. It is additionally, preferred to select the specificamount of ruthenium from within this broad weight range as a function ofthe amount of the platinum or palladium component, on an atomic basis,as is explained hereinafter.

This ruthenium component may be incorporated into the catalyticcomposite in any suitable manner known to those skilled in the catalystformulation art to result in a uniform dispersion of this component inthe carrier material. In addition, it may be added at any stage of thepreparation of the composite -- either during preparation of the carriermaterial or thereafter -- and the precise method of incorporation usedis not deemed to be critical so long as this component is relativelyuniformly distributed throughout the carrier material. One acceptableprocedure for incorporating this component into the composite involvescogelling or coprecipitating the ruthenium component during thepreparation of the preferred carrier material, alumina. This procedureusually comprehends the addition of a soluble, decomposable compound ofruthenium such as ruthenium tetrachloride, ruthenium tetrabromide,ruthenium tetraoxide and the like to the alumina hydrosol before it isgelled. The resulting mixture is then finished by conventional gelling,aging, drying and calcination steps as explained hereinbefore. A morepreferred way of incorporating this component is an impregnation stepwherein the porous carrier material is impregnated with a suitableruthenium containing-solution either before, during or after the carriermaterial is calcined. Preferred impregnation solutions are aqueoussolutions of water soluble, decomposable ruthenium compounds producingruthenium-containing complex anions in aqueous solutions such asammonium chlororuthenate, potassium chlororuthenate, potassiumruthenate, chlororuthenic (IV) acid, chlororuthenic (III) acid, and thelike complex compounds. Best results are ordinarily obtained when theimpregnation solution is an aqueous solution of chlororuthenic acid orammonium chlororuthenate. This component can be added to the carriermaterial either prior to, simultaneously with or after the othermetallic components are combined therewith. Best results are usuallyachieved when this component is added simultaneously with the platinumor palladium component.

Yet another essential ingredient of the catalyst used in the presentinvention is the alkali metal or alkaline earth metal component. Morespecifically, this component is selected from the group consisting ofthe compounds of the alkali metals -- cesium, rubidium, potassium,sodium, and lithium -- and of the alkaline earth metals -- calcium,strontium, barium, and magnesium. This component exists within thecatalytic composite in an oxidation state above that of the elementalmetal such as a relatively stable compound such as the oxide or sulfide,or in combination with one or more of the other components of thecomposite, or in combination with the carrier material such as, forexample, in the form of a metal aluminate. Since, as is explainedhereinafter, the composite containing the alkali metal or alkaline earthmetal is always calcined in an air atmosphere before use in theconversion of hydrocarbons, the most likely state this component existsin during use in the dehydrogenation reaction is the correspondingmetallic oxide such as lithium oxide, potassium oxide, sodium oxide andthe like. Regardless of what precise form in which it exists in thecomposite, the amount of this component utilized is preferably selectedto provide a composite containing about 0.1 to about 5 wt. % of thealkali or alkaline earth metal, and, more preferably, about 0.25 toabout 3.5 wt. %. Best results are obtained when this component is acompound of lithium or potassium. The function of this component is toneutralize any of the acidic materials which may have been used in thepreparation of the present catalyst so that the final catalyst isnonacidic.

This alkali metal or alkaline earth metal component may be combined withthe porous carrier material in any manner known to those skilled in theart to result in a relatively uniform dispersion of this componentthroughout the carrier material with consequential neutralization of anyacidic sites which may be present therein. Typically good results areobtained when it is combined by impregnation, coprecipitation,ion-exchange, and the like procedures. The preferred procedure, however,involves impregnation of the carrier material either before, during orafter it is calcined, or before, during or after the other metallicingredients are added to the carrier material. Best results areordinarily obtained when this component is added to the carrier materialafter the other metallic components because the alkali metal or alkalineearth metal acts to neutralize the acid used in the preferredimpregnation procedure for these metallic components. In fact, it ispreferred to add the platinum or palladium, ruthenium and Group IVAmetallic components to the carrier material, oxidize the resultingcomposite in an air stream at a high temperature (i.e., typically about600 to 1000° F.), then treat the resulting oxidized composite with amixture of air and steam in order to remove at least a portion of anyresidual acidity and thereafter add the alkali metal or alkaline earthmetal component. Typically, the impregnation of the carrier materialwith this component is performed by contacting the carrier material witha solution of a suitable decomposable compound or salt of the desiredalkali or alkaline earth metal. Hence, suitable compounds include thealkali metal or alkaline earth metal halides, sulfates, nitrates,acetates, carbonates, phosphates, and the like compounds. For example,excellent results are obtained by impregnating the carrier materialafter the platinum or palladium, ruthenium and Group IVA metalliccomponents have been combined therewith, with an aqueous solution oflithium nitrate or potassium nitrate.

Regarding the preferred amounts of the various metallic components ofthe subject catalyst, I have found it to be a good practice to specifythe amounts of the ruthenium component, the Group IVA metallic componentand the alkali or alkaline earth metal component, as a function of theamount of the platinum or palladium component. On this basis, the amountof the ruthenium component is ordinarily selected so that the atomicratio of ruthenium to platinum or palladium metal is about 0.1:1 toabout 10:1 with the preferred range being about 0.25:1 to 3:1.Similarly, the amount of the Group IVA metallic component is ordinarilyselected to produce a composite having an atomic ratio of Group IVAmetal to platinum or palladium metal within the broad range of about0.05:1 to 10:1. However, for the Group IVA metal to platinum group metalratio, the best practice is to select this ratio on the basis of thefollowing preferred range for the individual species: (1) for germanium,it is about 0.3:1 to 10:1, with the most preferred range being about0.6:1 to about 6:1; (2) for tin, it is about 0.1:1 to 3:1, with the mostpreferred range being about 0.5:1 to 1.5:1; and (3) for lead, it isabout 0.05:1 to 0.9:1, with the most preferred range being about 0.1:1to 0.75:1. Similarly, the amount of the alkali or alkaline earth metalcomponent is ordinarily selected to produce a composite having an atomicratio of alkali or alkaline earth metal to platinum or palladium metalof about 5:1 to about 50:1 or more, with the preferred range being about10:1 to about 25:1.

Another significant parameter for the instant catalyst is the "totalmetals content" which is defined to be the sum of the platinum orpalladium component, the ruthenium component, the Group IVA metalliccomponent, and the alkali or alkaline earth metal component, calculatedon an elemental metal basis. Good results are ordinarily obtained withthe subject catalyst when this parameter is fixed at a value of about0.2 to about 5 wt. %, with best results ordinarily achieved at a metalsloading of about 0.4 to about 4 wt. %.

Integrating the above discussion of each of the essential components ofthe catalytic composite used in the present invention, it is evidentthat a particularly preferred catalytic composite comprises acombination of a platinum component, a ruthenium component, a Group IVAmetallic component and an alkali or alkaline earth metal component withan alumina carrier material in amounts sufficient to result in thecomposite containing from about 0.05 to about 1 wt. % platinum, about0.05 to about 1 wt. % ruthenium, about 0.05 to about 2 wt. % of theGroup IVA metal and about 0.25 to about 3.5 wt. % of the alkali metal oralkaline earth metal.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the resulting multimetalliccomposite generally will be dried at a temperature of about 200° F. toabout 600° F. for a period of from about 2 to 24 hours or more, andfinally calcined or oxidized at a temperature of about 600° F. to about1100° F. in an air atmosphere for a period of about 0.5 to 10 hours,preferably about 1 to about 5 hours, in order to convert substantiallyall the metallic components to the corresponding oxide form. When acidiccomponents are present in any of the reagents used to effectincorporation of any one of the components of the subject composite, itis a good practice to subject the resulting composite to a hightemperature treatment with steam or with a mixture of steam and air,either before, during or after the oxidation step described above, inorder to remove as much as possible of the undesired acidic component.For example, when the platinum or palladium component is incorporated byimpregnating the carrier material with chloroplatinic acid, it ispreferred to subject the resulting composite to a high temperaturetreatment with steam in order to remove as much as possible of theundesired chloride.

The resultant oxidized multimetallic calcined catalytic composite ispreferably subjected to a substantially water-free reduction step priorto its use in the conversion of hydrocarbons. This step is designed toinsure a uniform and finely divided dispersion of the metalliccomponents throughout the carrier material. Preferably, substantiallypure and dry hydrogen (i.e., less than 20 vol. ppm. H₂ O) is used as thereducing agent in this step. The reducing agent is contacted with theoxidized composite at a temperature of about 800° F. to about 1200° F.,a gas hourly space velocity of about 100 to about 5,000 hr.⁻¹, and for aperiod of time of about 0.5 to 10 hours or more, effective to reduce atleast substantially all the platinum or palladium and rutheniumcomponents to the corresponding elemental metallic state whilemaintaining substantially all of the alkali or alkaline earth metalcomponent and the Group IVA component in a positive oxidation state.This reduction treatment may be performed in situ as part of a start-upsequence if precautions are taken to predry the plant to a substantiallywater-free state and if substantially water-free hydrogen is used.

The resulting selectively reduced multimetallic catalytic composite may,in some cases, be beneficially subjected to a presulfiding operationdesigned to incorporate in the catalytic composite from about 0.05 toabout 0.5 wt. % sulfur calculated on an elemental basis. Preferably,this presulfiding treatment takes place in the presence of hydrogen anda suitable sulfiding reagent (i.e. a metallic sulfide-producing reagent)which is usually a sulfur-containing decomposable compound such ashydrogen sulfide, lower molecular weight mercaptans, organic sulfides,etc. Typically this procedure comprises treating the selectively reducedcatalyst with a sulfiding gas such as a mixture containing a mole ratioof H₂ to H₂ S of about 10:1 at conditions sufficient to effect thedesired incorporation of sulfur, generally including a temperatureranging from about 50° F. up to about 1100° F. or more. Thispresulfiding step can be performed in situ or ex situ.

According to the method of the present invention, the dehydrogenatablehydrocarbon is contacted with the instant multimetallic catalyticcomposite in a dehydrogenation zone maintained at dehydrogenationconditions. This contacting may be accomplished by using the catalyst ina fixed bed system, a moving bed system, a fluidized bed system, or in abatch type operation; however, in view of the danger of attrition lossesof the valuable catalyst and of well-known operation advantages, it ispreferred to use a fixed bed system. In this system, the hydrocarbonfeed stream is preheated by any suitable heating means to the desiredreaction temperature and then passed into a dehydrogenation zonecontaining a fixed bed of the catalyst type previously characterized. Itis, of course, understood that the dehydrogenation zone may be one ormore separate reactors with suitable heating means therebetween toinsure that the desired conversion temperature is maintained at theentrance to each reactor. It is also to be noted that the reactants maybe contacted with the catalyst bed in either upward, downward, or radialflow fashion, with the latter being preferred. In addition, it is to benoted that the reactants may be in the liquid phase, a mixedliquid-vapor phase, or a vapor phase when they contact the catalyst,with best results obtained in the vapor phase.

Although hydrogen is the preferred diluent for use in the subjectdehydrogenation method, in some cases other art-recognized diluents maybe advantageously utilized such as steam, methane, carbon dioxide, andthe like diluents, Hydrogen is preferred because it serves thedual-function of not only lowering the partial pressure of thedehydrogenatable hydrocarbon, but also of suppressing the formation ofhydrogen-deficient, carbonaceous deposits on the catalytic composite.Ordinarily, hydrogen is utilized in amounts sufficient to insure ahydrogen to hydrocarbon mole ratio of about 1:1 to about 20:1, with bestresults obtained in the range of about 1.5:1 to about 10:1. The hydrogenstream charged to the dehydrogenation zone will typically be recyclehydrogen obtained from the effluent stream from this zone after asuitable separation step.

When hydrogen is used as a diluent, a preferred practice is to add wateror a water-producing substance to the dehydrogenation zone. This wateradditive may be included in the charge stock, or in the hydrogen stream,or in both of these, or added independently of these. Ordinarily, it ispreferred to inject the necessary water by saturating at least a portionof the input hydrogen stream with water. Good results are also obtainedwhen a water-producing substance such as a C₂ to C₈ alcohol, ether,ketone, aldehyde or the like oxygen-containing decomposable organiccompound is added to the charge stock. Regardless of the source of thewater, the amount of equivalent water added should be sufficient tomaintain the total amount of water continuously entering thedehydrogenation zone in the range of about 50 to about 10,000 wt. ppm.of the hydrocarbon charge stock, with best results obtained at a levelcorresponding to about 1500 to 5000 wt. ppm. of the charge stock.

Concerning the conditions utilized in the process of the presentinvention, these are generally selected from the conditions well knownto those skilled in the art for the particular dehydrogenatablehydrocarbon which is charged to the process. More specifically, suitableconversion temperatures are selected from the range of about 700 toabout 1200° F., with a value being selected from the lower portion ofthis range for the more easily dehydrogenated hydrocarbons such as thelong chain normal paraffins and from the higher portion of this rangefor the more difficultly dehydrogenated hydrocarbons such as propane,butane, and the like hydrocarbons. For example, for the dehydrogenationof C₆ to C₃₀ normal paraffins, best results are ordinarily obtained at atemperature of about 800 to about 950° F. The pressure utilized isordinarily selected at a value which is as low as possible consistentwith the maintenance of catalyst stability, and is usually about 0.1 toabout 10 atmospheres, with best results ordinarily obtained in the rangeof about .5 to about 3 atmospheres. In addition, a liquid hourly spacevelocity (calculated on the basis of the volume amount, as a liquid, ofhydrocarbon charged to the dehydrogenation zone per hour divided by thevolume of the catalyst bed utilized) is selected from the range of about1 to about 40 hr.⁻¹, with best results for the dehydrogenation of longchain normal paraffins typically obtained at a relatively high spacevelocity of about 25 to 35 hr.⁻¹.

Regardless of the details concerning the operation of thedehydrogenation step, an effluent stream will be withdrawn therefrom.This effluent will contain unconverted dehydrogenatable hydrocarbons,hydrogen, and products of the dehydrogenation reaction. This stream istypically cooled and passed to a separating zone wherein a hydrogen-richvapor phase is allowed to separate from a hydrocarbon-rich liquid phase.In general, it is usually desired to recover the unreacteddehydrogenatable hydrocarbon from this hydrocarbon-rich liquid phase inorder to make the dehydrogenation process economically attractive. Thisrecovery step can be accomplished in any suitable manner known to theart such as by passing the hydrocarbon-rich liquid phase through a bedof suitable adsorbent material which has the capability to selectivelyretain the dehydrogenated hydrocarbons contained therein or bycontacting same with a solvent having a high selectivity for thedehydrogenated hydrocarbon or by a suitable fractionation scheme werefeasible. In the case where the dehydrogenated hydrocarbon is amono-olefin, suitable adsorbents having this capability are activatedsilica gel, activated carbon, activated alumina, various types ofspecially prepared zeolitic crystalline alumino-silicate molecularsieves, and the like adsorbents. In another typical case, thedehydrogenated hydrocarbons can be separated from the unconverteddehydrogenatable hydrocarbons by utilizing the inherent capability ofthe dehydrogenated hydrocarbons to enter into several well-knownchemical reactions such as alkylation, oligomerization, halogenation,sulfonation, hydration, oxidation, and the like reactions. Irrespectiveof how the dehydrogenated hydrocarbons are separated from the unreactedhydrocarbons, a stream containing the unreacted dehydrogenatablehydrocarbons will typically be recovered from this hydrocarbonseparation step and recycled to the dehydrogenation step. Likewise, thehydrogen phase present in the hydrogen separating zone will be withdrawntherefrom, a portion of it vented from the system in order to remove thenet hydrogen make, and the remaining portion is typically recycled,through suitable compressing means, to the dehydrogenation step in orderto provide diluent hydrogen therefor.

In a preferred embodiment of the present invention wherein long chainnormal paraffin hydrocarbons are dehydrogenated to the correspondingnormal mono-olefins, a preferred mode of operation of this hydrocarbonseparation step involves an alkylation reaction. In this mode, thehydrocarbon-rich liquid phase withdrawn from the separating zone iscombined with a stream containing an alkylatable aromatic and theresulting mixture passed to an alkylation zone containing a suitablehighly acidic catalyst such as an anhydrous solution of hydrogenfluoride. In the alkylation zone the mono-olefins react with thealkylatable aromatic while the unconverted normal paraffins remainsubstantially unchanged. The effluent stream from the alkylation zonecan then be easily separated, typically by means of a suitablefractionation system, to allow recovery of the unreacted normalparaffins. The resulting stream of unconverted normal paraffins is thenusually recycled to the dehydrogenation step of the present invention.

The following working examples are introduced to illustrate further thenovelty, mode of operation, utility and benefits associated with thedehydrogenation method and the nonacidic multimetallic catalyticcomposite of the present invention. These examples are intended to beillustrative rather than restrictive.

These examples are all performed in a laboratory scale dehydrogenationplant comprising a reactor, a hydrogen separating zone, a heating means,cooling means, pumping means, compressing means, and the like equipment.In this plant the feed stream containing the dehydrogenatablehydrocarbon is combined with a hydrogen stream and the resultant mixtureheated to the desired conversion temperature, which refers herein to thetemperature maintained at the inlet to the reactor. The heated mixtureis then passed into contact with the catalyst which is maintained as afixed bed of catalyst particles in the reactor. The pressures reportedherein are recorded at the outlet from the reactor. An effluent streamis withdrawn from the reactor, cooled, and passed into the separatingzone wherein a hydrogen gas phase separates from a hydrocarbon-richliquid phase containing dehydrogenated hydrocarbons, unconverteddehydrogenatable hydrocarbons and a minor amount of side products of thedehydrogenation reaction. A portion of the hydrogen-rich gas phase isrecovered as excess recycle gas with the remaining portion beingcontinuously recycled through suitable compressive means to the heatingzone as described above. The hydrocarbon-rich liquid phase from theseparating zone is withdrawn therefrom and subjected to analysis todetermine conversion and selectivity for the desired dehydrogenatedhydrocarbon as will be indicated in the examples. Conversion numbers ofthe dehydrogenatable hydrocarbon reported herein are all calculated onthe basis of disappearance of the dehydrogenatable hydrocarbon and areexpressed in mole percent. Similarly, selectivity numbers are reportedon the basis of moles of desired hydrocarbon produced per 100 moles ofdehydrogenatable hydrocarbon converted.

All of the catalysts utilized in these examples are prepared accordingto the following general method with suitable modifications instoichiometry to achieve the compositions reported in each example.First, a tin-containing alumina carrier material comprising 1/16 inchspheres having an apparent bulk density of about 0.3 g/cc is preparedby: forming an aluminum hydroxyl chloride sol by dissolvingsubstantially pure aluminum pellets in a hydrochloric acid solution,adding stannic chloride to the resulting sol in an amount selected toresult in a finished catalyst containing 0.4 wt. % tin, addinghexamethylenetetramine to the resulting tin-containing sol, gelling theresulting mixture by dropping it into an oil bath to form sphericalparticles of a tin-containing alumina hydrogel, aging, and washing theresulting particles with an ammoniacal solution and finally drying,calcining, and steaming the aged and washed particles to form sphericalparticles of gamma-alumina containing a uniform dispersion of about 0.4wt. % tin in the form of tin oxide and substantially less than 0.1 wt. %combined chloride. Additional details as to this method of preparingthis alumina carrier material are given in the teachings of U.S. Pat.No. 2,620,314.

An aqueous impregnation solution containing chloroplatinic acid,chlororuthenic acid and nitric acid is then prepared. The impregnationsolution is then used to impregnate the tin-containing gamma-aluminaparticles. The amounts of the various reagents contained in theimpregnation solution are carefully selected to yield final catalyticcomposites containing a uniform dispersion of the required amounts ofplatinum and ruthenium as reported in the examples. In order to insureuniform distribution of metallic components throughout the carriermaterial, this impregnation step is performed by adding the aluminaparticles to the impregnation mixture with constant agitation. Theimpregnation mixture is maintained in contact with the alumina particlesfor a period of about 1/2 hour at a temperature of 70° F. thereafter,the temperature of the impregnation mixture is raised to about 225° F.and the excess solution is evaporated in a period of about one hour. Theresulting dried particles are then subjected to an oxidation treatmentin an air atmosphere at a temperature of about 500 to about 1000° F. forabout 2 to 10 hours effective to convert substantially all of themetallic components to the corresponding metallic oxides. Thereafter,the resulting oxidized particles are treated with an air streamcontaining from about 10 to about 30% steam at a temperature of about800 to about 1000° F. for an additional period from about 1 to about 10hours in order to reduce the residual combined chloride in the compositeto a level corresponding to less than about 0.2 wt. % thereof.

Finally, the alkali or alkaline earth metal component is added to theresulting oxidized and steamed particles in a second impregnating step.This second impregnation step involves contacting the oxidized particleswith an aqueous solution of a suitable decomposable salt of the desiredalkali or alkaline earth metal component. For the composites utilized inthe present examples, the salt is either lithium nitrate or potassiumnitrate. The amount of this salt is carefully chosen to result in afinal composite having the desired nonacidic characteristics. Theresulting alkali impregnated particles are then dried, calcined andsteamed in exactly the same manner as described above following thefirst impregnation step. In some cases, it is possible to combine bothof these impregnation steps into a single step, thereby significantlyreducing the time and complexity of the catalyst manufacturingprocedure.

In all the examples the catalyst is selectively reduced during start-upby contacting with a substantially water-free hydrogen stream at anelevated temperature of about 900 to 1100° F. for a period of timesufficient to reduce substantially all of the platinum and rutheniumcomponents to the elemental state while maintaining the tin and alkalior alkaline earth metal components in a positive oxidation state.

EXAMPLE I

The reactor is loaded with 100 cc of a catalyst containing, on anelemental basis, 0.375 wt. % platinum, 0.375 wt. % ruthenium, 0.4 wt. %tin, 0.5 wt. % lithium and less than 0.2 wt. % chloride. The feed streamutilized is commercial grade isobutane containing 99.7 wt. % isobutaneand 0.3 wt. % normal butane. The feed stream is contacted with thecatalyst at a temperature of 1065° F., a pressure of 10 psig, a liquidhourly space velocity of 4.0 hr.⁻¹ and a hydrogen to hydrocarbon moleratio of 2:1. The dehydrogenation plant is lined-out at these conditionsand a 20 hour test period commenced. The hydrocarbon product stream fromthe plant is continuously analyzed by GLC (gas-liquid chromatography)and a high conversion of isobutane is observed with good selectivity forisobutylene.

EXAMPLE II

The catalyst contains, on an elemental basis, 0.25 wt. % platinum, 0.25wt. % ruthenium, 0.4 wt. % tin, 0.5 wt. % lithium, and less than 0.2 wt.% combined chloride. The feed stream is commercial grade normaldodecane. The dehydrogenation reactor is operated at a temperature of870° F., a pressure of 10 psig., a liquid hourly space velocity of 32hr.⁻¹ and a hydrogen to hydrocarbon mole ratio of 8:1. After a line-outperiod, a 20 hour test period is performed during which the averageconversion of the normal dodecane is maintained at a high level with aselectivity for dodecene of above 90%.

EXAMPLE III

The catalyst is the same as utilized in Example II. The feed stream isnormal tetradecane. The conditions utilized are a temperature of 840°F., a pressure of 20 psig., a liquid hourly space velocity of 32 hr.⁻¹,and a hydrogen to hydrocarbon mole ratio of 8:1. After a line-outperiod, a 20 hour test shows an average conversion of approximately 12%and a selectivity for tetradecene of above about 90%.

EXAMPLE IV

The catalyst contains, on an elemental basis, 0.2 wt. % platinum, 0.1wt. % ruthenium, 0.4 wt. % tin, 0.6 wt. % lithium and combined chloridebeing less than 0.2 wt. %. The feed stream is substantially purecyclohexane. The conditions utilized are a temperature of 950° F., apressure of 100 psig., a liquid hourly space velocity of 3.0 hr.⁻¹ and ahydrogen to hydrocarbon mole ratio of 5:1. After a line-out period, a 20hour test is performed and almost quantitative conversion of thecyclohexane to benzene and hydrogen is observed.

EXAMPLE V

The catalyst contains, on an elemental basis, 0.2 wt. % platinum, 0.2wt. % ruthenium, 0.4 wt. % tin, 2.8 wt. % potassium and less than 0.2wt. % combined chloride. The feed stream is commercial gradeethylbenzene. The conditions utilized are a pressure of 15 psig., aliquid hourly space velocity of 32 hr.⁻¹, a temperature of 950° F., anda hydrogen to hydrocarbon mole ratio of 8:1. During a 20 hour testperiod, at least 85% of equilibrium conversion of ethylbenzene isobserved with high selectivity for styrene.

It is intended to cover by the following claims all changes andmodifications of the above disclosure of the present invention thatwould be self-evident to a man of ordinary skill in the catalystformulation art or in the hydrocarbon dehydrogenation art.

I claim as my invention:
 1. A method for dehydrogenating adehydrogenatable hydrocarbon comprising contacting the hydrocarbon, atdehydrogenation conditions, with a nonacidic catalytic compositeconsisting essentially of a porous carrier material containing, on anelemental basis, about 0.01 to about 2 wt. % platinum or palladium,about 0.01 to 2 wt. % ruthenium, about 0.01 to about 5 wt. % Group IVAmetal and about 0.1 to about 5 wt. % of an alkali metal or alkalineearth metal; wherein the platinum or palladium, ruthenium, Group IVAmetal and alkali metal or alkaline earth metal are uniformly dispersedthroughout the porous carrier material; wherein substantially all of theplatinum or palladium and ruthenium are present in the elementalmetallic state; and wherein substantially all of the Group IVA metal andalkali metal or alkaline earth metal are present in an oxidation stateabove that of the elemental metal.
 2. A method as defined in claim 1wherein the porous carrier material is a refractory inorganic oxide. 3.A method as defined in claim 2 wherein the refractory inorganic oxide isalumina.
 4. A method as defined in claim 1 wherein the alkali metal oralkaline earth metal is lithium.
 5. A method as defined in claim 1wherein the alkali metal or alkaline earth metal is potassium.
 6. Amethod as defined in claim 1 wherein the Group IVA metal is germanium.7. A method as defined in claim 1 wherein the Group IVA metal is tin. 8.A method as defined in claim 1 wherein the Group IVA metal is lead.
 9. Amethod as defined in claim 1 wherein the atomic ratio of Group IVA metalto platinum or palladium is about 0.05:1 to about 10:1, wherein theatomic ratio of ruthenium to platinum or palladium is about 0.1:1 toabout 10:1 and wherein the atomic ratio of the alkali metal or alkalinemetal to platinum group metal is about 5:1 to 50:1.
 10. A method asdefined in claim 6 wherein substantially all of the germanium is presentas germanium oxide.
 11. A method as defined in claim 7 whereinsubstantially all of the tin is present as tin oxide.
 12. A method asdefined in claim 8 wherein substantially all of the lead is present aslead oxide.
 13. A method as defined in claim 1 wherein the compositecontains, on an elemental basis, about 0.05 to about 1 wt. % platinum orpalladium, about 0.05 to about 1 wt. % ruthenium, about 0.05 to about 2wt. % Group IVA metal and about 0.25 to about 3.5 wt. % alkali metal oralkaline earth metal and wherein the porous carrier material is alumina.14. A method as defined in claim 1 wherein said dehydrogenatablehydrocarbon is admixed with hydrogen when it contacts the catalyticcomposite.
 15. A method as defined in claim 1 wherein saiddehydrogenatable hydrocarbon is an aliphatic hydrocarbon containing 2 to30 carbon atoms per molecule.
 16. A method as defined in claim 1 whereinsaid dehydrogenatable hydrocarbon is a normal paraffin hydrocarboncontaining about 4 to 30 carbon atoms per molecule.
 17. A method asdefined in claim 1 wherein said dehydrogenatable hydrocarbon is a normalparaffin hydrocarbon containing about 10 to about 18 carbon atoms permolecule.
 18. A method as defined in claim 1 wherein saiddehydrogenatable hydrocarbon is an alkylaromatic, the alkyl group ofwhich contains 2 to 6 carbon atoms.
 19. A method as defined in claim 1wherein said dehydrogenatable hydrocarbon is a naphthene.
 20. A methodas defined in claim 1 wherein said dehydrogenation conditions include atemperature of about 700 to about 1200° F., a pressure of about 0.1 toabout 10 atmospheres, a liquid hourly space velocity of about 1 to 40hr.⁻¹ and a hydrogen to hydrocarbon mole ratio of about 1:1 to about20:1.
 21. A method as defined in claim 1 wherein the contacting isperformed in the presence of water or a water-producing substance in anamount corresponding to about 50 to about 10,000 wt. ppm. based onhydrocarbon charged.